This invention relates to a method and apparatus for the formation of a laminate web of indefinite length, the laminate characterized by two outer or facing paperboard webs which are adhered to and sandwich a middle embossed or dimpled paperboard web. Such laminates are useful for making paperboard boxes.
It is known to form a three layer combined board or three layer laminate from two outer or facing layers and an inner undulating or corrugated layer. Sometimes the inner layer is corrugated and assumes the general form of a sine wave, or assumes the form of dimples, with the dimples either extending outwardly from one side only of the middle layer, or outwardly from both sides. However, the formation of such a combined board or laminate having embossments or dimples extending on both sides is difficult to carry out. A basic manufacturing problem is that of drying of the middle layer as it is being deformed, i.e., as the dimples or corrugations are formed. In the case of vacuum drum deformation, wherein one or more vacuum drums having apertures on their respective surfaces would be employed, the drying of the paperboard as it is being deformed into the drum apertures would present a problem, namely, the lack of desired flexibility and ductility of the paperboard to thereby permit deformation into dimples or embossments having the same height. This problem would become more accentuated wherein one vacuum drum was used to provide dimples or embossments on one surface of the web, while a second vacuum drum was used to form embossments on the other surface. During the formation of the first group or set of embossments, the paperboard would be dried out by the passage of air through it, due to the vacuum formation process, i.e., the porous character of the paperboard. By the time the paperboard reached the second vacuum drum, the paperboard would be significantly dried and is hence even less flexible and thereby more difficult to deform and hence more apt to tear or rip.